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Monday, January 17, 2011

Here's the new definition of asthma

As you can see from last Monday's post, the definition of asthma is constantly changing. This is a good thing, because it means we're getting smarter. It means we're getting closer to getting this disease under control, and it may some day mean a cure.

Even during my short lifespan the definition of asthma has changed quite a bit. It's important we asthmatics keep up on the current definition, because how asthma is treated is dependent on how it's defined.

In 1985 I was taught the acronym ROAD to easily define asthma, which stands for Reversible Obstructive Airway Disease. ROAD's still valid, yet no longer complete.

Today we know asthma is still ROAD, yet it's also a disease where the air passages in your lungs (called bronchioles) are chronically (always) inflamed or swollen, and thus are very sensitive to various stimuli called asthma triggers.

When exposed to asthma triggers, this inflammation becomes worse and the muscles (bronchial muscles) surrounding the bronchioles spasm (called bronchospasm) and this narrows the bronchioles, thus trapping air in your lungs.

This process is called an acute (happening right now) asthma attack, also called an asthma flare, or an asthma exacerbation. (View normal & asthmatic lung here).

Another thing that may occur during an attack, which narrows the bronchioles even further, and thus exacerbates this problem, is that cells lining your air passages secrete excess secretions. If this process becomes severe, this mucus may become thick and actually block the air passages. This is called a mucus plug.

As this process worsens, this air trapping may cause a progressive hyperinflation of the lungs, making the asthmatic appear to have hunched shoulders and an increase diameter of the chest (see picture). Another reason for hunched shoulders is the patient's attempt to make more room for air exchange.

All these processes ultimately increase the patient's work of breathing. It may feel as though you can't get air in, but you are really having trouble getting trapped air out.

These patients may actually lean on things to breath, and children often present in the emergency room with their fingers clenched into the side of the bed, shoulders high, in what we like to call the frog position.

Between asthma episodes, however, most asthmatics have no symptoms, and can live normal, active lives. This, ultimately, is the goal of asthma therapy: to minimize symptoms.

The key component of asthma is that this entire process is completely reversible. Sometimes symptoms are mild and they resolve on their own. Other times medicines are needed and occasionally more invasive therapies.

There are three types of asthma:

1. Intrinsic: This is where the stimuli that trigger your asthma are anything but allergies. Most of the people with this type of asthma have adult onset asthma. Some examples are chemicals inhaled via cigarette smoke, chemicals inhaled at work or home (such as from household cleaners), strong smells, humidity, aspirin, emotions, stress, chest infections, GERD, and exercise induced bronchospasm.

2. Extrinsic: This is where the stimuli that trigger asthma come from allergens. Some examples include dust mites, cockroach urine, mold, fungus, pollen, grass, trees and animal dander. Since 70 percent of asthmatics also have allergies, this type of asthma is often called allergic asthma or atopic asthma. Most asthmatics diagnosed with childhood onset asthma have this type.

3. Mixed: Many asthmatics, me included, have a combination of intrinsic and extrinsic.

Back when ROAD was taught, the goal of asthma therapy was to treat acute symptoms (as I wrote about here). With our new asthma wisdom the goal is to prevent asthma, yet to have a plan to treat acute symptoms when they do occur.

So, current treatment for asthma focuses on the two main components of asthma: Acute bronchospasm and Chronic Inflammation. Yet there are actually four possible components of asthma:

It's recommended that every asthmatic at least have a rescue inhaler on his or her possession at all times. Asthma is usually considered controlled if you have fewer than two to three acute asthma episodes in a two week period, however there are exceptions.

Some asthmatics only need to carry a rescue inhaler to treat their symptoms which occur rarely. However, a majority require controller medicines to prevent asthma attacks.

If these alone do not control asthma, a leukotreine blocker (like Singulair and Accolate) may be prescribed to control inflammation and block the allergy response. For some, Singulair alone controls asthma.

3. Combination: Many asthmatics use combination inhalers such as Advair and Symbicort, which have both an inhaled corticosteroid to control inflammation and a long acting beta adrenergic to prevent bronchospasm. Actually, this is currently the most common approach to treating asthma.

4. Airway remodeling: Asthma experts recommend asthma be swiftly diagnosed and treated. When asthma is not treated over a long period of time permanent airway changes can result, and this often leads to severe asthma or COPD. This type involves less than 10 percent of asthma cases, and treatment is generally more complicated.

So our current definition is a disease of chronic inflammation that worsens and causes bronchospasm, airway obstruction, and air trapping when you're exposed to your asthma triggers. Acute bronchospasmcan be reversed, and inflammation can be treated with asthma controller meds.

Ultimately, with good asthma control, most asthmatics should be able to live normal, active lives.